Job Scheduling

Problem Background

John has far too much work to do.

To keep the farm running efficiently, he must earn money from his work, and each job takes one unit of time.

His workday starts at time $0$ and has $10^9$ units of time in total.

At any moment he may choose to do any one of the $N$ jobs numbered $1$ to $N$.

Each job has a deadline: for the $i$-th job there is a deadline $D_i$, and if he completes it he earns a profit $P_i$.

Given the profits and deadlines, what is the maximum profit John can obtain?

Input Format

The first line contains an integer $N$.

Lines $2$ to $N+1$ each contain two integers $D_i$ and $P_i$.

Output Format

One number: the maximum profit.

Sample Input

3 
2 10 
1 5 
1 7

Sample Output

17

Constraints

$1 \le N \le 1 \times 10^5$.

$0 \le D_i, P_i \le 1 \times 10^9$.